Such a circuit arrangement and such a method are known e.g. from DE 103 46 693 A1. The known circuit arrangements serves for actuating a piezo valve used for controlling a closed-off volume of air. The valve can provide e.g. the three states “filling”, “maintaining pressure” and “venting”.
In the case of the piezo valve actuated by the known circuit arrangement, the two piezo actuators form a piezo stack composed of two piezoelectrically active components acting in opposite senses, in order to enable a deflection in both directions (transversely with respect to the longitudinal direction) with respect to an undeflected rest position.
Such piezo valves very generally have diverse fields of application. Such valves can be used very advantageously for example as controllable air valves in systems for changing the contour of motor vehicles seats.
One fundamental problem on using a piezoelectric bending transducer (“piezo bender”) as actuator in a piezo valve is that the bending transducer constitutes a system having more or less pronounced mechanical resonances and can thus perform undesirable vibrations.
Such vibrations of the bending transducer can constitute an impediment of the quantitative valve function (setting of a precise degree of opening of the valve). Further disadvantageous effects are e.g. development of noise that is undesirable in many fields of application and/or an inherently unnecessary additional mechanical loading of the bending transducer.
Undesirable vibrations of the bending transducer can be brought about e.g. on account of relatively abrupt valve actuation processes. Moreover, even in the case of slow or unchanged degree of opening of the valve, such vibrations can also be brought about by the (turbulent) mass flow flowing through the valve.
The flow of the relevant medium (e.g. air, hydraulic oil, etc.) through the valve produces an excitation that is broadband in terms of frequency, whereby primarily the mechanical resonant frequencies of the bending transducer can be excited (mouth organ effect). This effect occurs to different degrees depending on the instantaneous operating conditions (inlet pressure, back pressure, effective valve cross section, viscosity of the medium, mechanical bending travel limitation, etc.).